Wireless networks may be comprised of a large number of wireless devices ranging from complex and powerful computers to simple and inexpensive wireless communication entities such as wireless sensors and actuators. The wireless connectivity may also be different in different networks and multiple radio-access technologies, RATs, may also be used. The topology of the wireless networks may further range from traditional cellular networks where base stations and strong network control is employed, to so-called “ad-hoc” networks comprised of devices and nodes which communicate directly with each other in a “best-effort” manner using a shared radio resource in unlicensed spectra, sometimes referred to as Internet-of-Things, IoT, devices. This disclosure is directed to the latter type of network and it may be assumed that the traffic load is mostly low such that the shared radio resource is usually unoccupied and that, in spite of the uncoordinated ad-hoc transmissions, there will rarely be any collisions of transmissions occurring simultaneously.
As an example, multiple devices that are located within fairly close geographical proximity may transmit data and messages in an ad-hoc manner directly to neighboring nodes provided that they are within transmission range or “sensing distance”, meaning that the transmissions can be received and decoded properly. One of these nodes could be a gateway entity, connecting a group of wireless devices to the Internet or to a cellular network. All devices in such a scenario typically transmit on the same radio resource, e.g. frequency, and are thus able to decode all signals received. In this disclosure, a device that performs transmission of data is denoted “transmit device”, and the term “data” is used to denote any information or payload that a transmit device needs to transmit to another node.
In practice, the above scenario may e.g. be a home environment where battery-powered low-cost wireless temperature sensors are integrated with portable heating elements throughout the home. These sensors may respond by sending periodic temperature measurements to a central climate controller which in turn may send instructions to adjust the heating element settings, thereby regulating the home temperature. Additionally, the climate controller may convey the current local environment information to a remote smartphone via the Internet, e.g. to inform the home owner.
In a communication scenario where transmit devices communicate over a shared radio resource in the above manner, it may be assumed that the devices are mostly within each other's transmission range so that all transmissions can reach their destinations. Should the distances between the devices be too large for such direct communication, a relay device may be employed to forward all transmissions it receives, potentially with increased power, so as to improve the communication coverage in the network.
FIG. 1 illustrates an example of the above-described scenario where various transmit devices “D” of a wireless network perform transmissions of data where each transmission is addressed to another node, e.g. transmit device, that is typically, but not always, within transmission range to receive the transmission and recognize a destination identity in the transmission as its own identity. In this example however, one transmit device 100 transmits data addressed to another transmit device 102 which is too far away to be able to receive and decode the transmission which thus does not reach the intended destination. It is thus a problem that devices or nodes that are basically located out of transmission range of one another, e.g. at opposite ends of the network, are not able to communicate directly in the manner described above.
In order to overcome the above problem and increase the overall coverage of such a network, it is possible to employ a wireless node basically located “in the middle” that is configured to retransmit any transmissions it receives, thereby acting as a relay to extend the distance of the transmissions. In FIG. 1, a relay device 104 is employed which operates to perform such retransmissions, i.e. forwarding of transmissions it receives. In some implementations the relay device operates on all transmissions even when the original transmission alone would have been sufficient. As a result, a destination node may inefficiently receive two transmissions: first the original transmission from the transmit device and then a redundant identical transmission from the relay device.
To overcome these shortcomings, the relay device 104 can be configured to only forward transmissions of selected traffic from specific nodes, i.e., transmissions that actually require the forwarding functionality such as the above-mentioned transmission from device 100 to device 102. But this functionality can be quite complex to realize as it requires analysis and determination of radio channels between the different nodes and radio capabilities of the individual devices, etc. This is because it must be determined which transmissions need to be retransmitted by the relaying device so that other transmissions will not be retransmitted unnecessarily. As an example, if transmissions from a controller to an Internet gateway do not require relaying, but transmissions from the controller to a sensor do require relaying, then this needs to be determined and programmed into the relay device. Moreover, if transmit devices are moved it is necessary to perform the above analysis repeatedly, e.g. on a regular basis.
To conclude, employing a relay device to enlarge the radio coverage may be either complex to implement efficiently to achieve selective retransmissions only when needed, or it will result in great amounts of redundant retransmissions if they are not selective by forwarding all transmissions.